Check if Kubuntu is running on 64bit or 32bit machine

Run

uname -a

My machine gives this:

Linux james-desktop 2.6.38-11-generic #48-Ubuntu SMP Fri Jul 29 19:02:55 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux

It should be easy to figure out if your box is 32 bit or 64 bit from the string your box gives you.

This page says to run

$ grep flags /proc/cpuinfo

and if the lm flag (long mode, I think) is present, you have a 64-bit CPU. The same page also describes JamWaffles's answer of using the kernel's targeted architecture.

You can check what is your kubuntu architecture (a 64 bits or 32 machine) using terminal run

getconf WORD_BIT

It will show 32 or 64-bit kUbuntu.